Agreed about both taking very good pictures. The 7D under the right conditions performs just as well as its expensive brother. On the other hand, much of the advantage of crop in giving extra reach is illusory. I did some iso12233 chart tests at 100 iso with the 100-400mm L on both bodies as it is a very popular but not very sharp lens - its defects according to Plamen's analysis should show up more on the crop. At closer distances where the closely spaced lines on the chart are easily resolved, the 5D III gave clearer, more contrasty images. At long distances where the lines were at the limits of resolution, they were marginally better resolved by the 7D but IQ was much poorer from poorer contrast and so again the resultant overall image was not better.

The good news for the bird photography 7D owner is that you have camera that can equal the best (at lower iso).The good news for the bird photography 5D III or 1DX owner is that you are not really disadvantaged by not having the crop factor (but both owners probably don't need me to tell you that).

Put me down in the heron test in the camp of "full framed cropped 5d3 equals or exceeds 7d for bird photography". My test was similar to the herons except I used kingfishers in extreme range. The 5d3 images yielded better detail when cropped to equal framing. My settings for birds in flight are usually shutter 1250-1600, f 7.1 to 10 and ISo on automatic. With the 7d Letting the iso go above 320 in autoiso has its own issues.

So for me a ff has more sharpness than crop given the same lens and distance to target.

Once Canon releases a high mp FF body, there would be mo much need for crop cameras in term of IQ, but croppers could achieve higher fps for less $$ for those who need them.

I think that Canon should implement a crop mode in their future FF bodies to lower the size of the RAW files (but no need to take EF-S lenses), and keep the sRAW and mRAW options for those who do not want large (non cropped) RAWs. The Nikon compressed RAW format is another option.

It means that the sensor in D800 at APS mode = 15,3Mp has better pixels signal =they have a greater efficiency than the 7D.

If you are talking about Quantum Efficiency - it depends on the sensor technology, not on the number of the pixels. In my analysis, I am not taking the noise factor into account. Then, if you crop the D800 to APC size, you are just getting a cropped sensor, something like the 50D but with 1.5 crop factor.

I've read bits and pieces of this thread and I read a little of the math and whatnot, not much that I've understood, but what about the crucial question...print?

You have a small subject 50 yards away (you can't get closer) and a 300mm 2.8 lens attatched to that 7D/5dMkII manually prefocused. Now, that small subject will not fill the frame of either camera...you must crop to create an equal field of view and make a 30x30" print.

Which of those cameras is going to cough out the better print?

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